Effect of pressure on the crystallization behaviour of polyethylene terephthalate

Compression molding is a current technique in polymer processing. Despite numerous studies, effect of molding pressure on physical properties has surprisingly not been fully investigated. In this study, the thermal and mechanical behavior of the compression-molded polyethylene were thus explored to better grasp the relationship between processing parameters and ensuing properties. The effect of the molding temperature, pressure, cooling rate, and temperature profile on the tensile and flexural moduli as well as melting point of polyethylene was studied. We conclude that higher tensile and flexural moduli are obtained by increasing pressure and molding temperature, as well as decreasing the cooling rate. Our results were corroborated by X-ray diffraction and differential scanning calorimetry measurements. Moreover, the use of a temperature gradient with different temperatures for the upper and bottom plates of the mold leads to asymmetric samples whose tensile and flexural moduli are improved. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46176.

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Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

Shamloo

Fathi

Elkoun

et al. 2017

J of Applied Polymer Sci

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Morphology investigation on high‐pressure crystallized bisphenol‐A polycarbonate/dioctyl phthalate blends

Lü

Huang

2007

J Polym Sci B Polym Phys

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The high-pressure crystallized bisphenol-A polycarbonate/dioctyl phthalate (BAPC/DOP) blend samples were investigated using wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The specimens were prepared in a piston-cylinder high-pressure apparatus by varying the temperature, the pressure and the crystallization time for a BAPC/DOP (90/ 10, wt/wt) blend. The other four specimens were also prepared with different weight ratios of BAPC/DOP. The DSC results showed that the amorphous BAPC could be crystallized in 45 min by the blending with DOP and the subsequent high-pressure treatment. A wide variety of morphologies of BAPC crystals were disclosed by SEM, including spherulites, spatial dendrites, crystalbars, platelets and regular polygonal crystals of different characteristics. The folded-chain lamellar crystals were found to be the substructures of these observed BAPC microstructures. The SEM revealed a granular substructure of the lamellae in a low-crystallinity sample as well, which indicated that the crystallization of BAPC in the multiphase system might possibly agree with the model developed by Strobl.

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Behavior of pressure dependence of melting temperatures in aromatic polyesters: Influence of polymer structure

Rohindra

Tanaka

Kuboyama

et al. 2009

J Polym Sci B Polym Phys

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The thermal behavior of three aromatic polyesters in a homologous series, poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT) was studied under hydrostatic pressure up to 200 MPa by using a high pressure differential thermal analysis apparatus. Confining fluid high pressure dilatometer was used to establish the volume–temperature curves (in both solid and liquid regions) from which volume change on melting of these polyesters at atmospheric pressure was determined. Single endothermic peak was seen for PET and PTT, whereas PBT showed double peaks above 50 MPa. Pressure coefficient of melting temperature at atmospheric pressure (dTm/dp(0)), was obtained from the quadratic fit. The dTm/dp(0) for PTT was newly determined to be 0.445 KMPa−1, whereas for PET and PBT were 0.503 and 0.455 KMPa−1, respectively, comparable to reported values. The dTm/dp(0) exhibited the odd‐even behavior corresponding to odd and even number of methylene groups in the repeat unit. Enthalpy and entropy of fusion had the most influence on this coefficient. Entropy related to conformational and volume change were evaluated and the former was found to have a significant impact on the value of dTm/dp(0). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1799–1808, 2009

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Effect of pressure on the crystallization behaviour of polyethylene terephthalate

Cited by 5 publications

References 19 publications

Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

Morphology investigation on high‐pressure crystallized bisphenol‐A polycarbonate/dioctyl phthalate blends

Behavior of pressure dependence of melting temperatures in aromatic polyesters: Influence of polymer structure

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